It always feels like a waste of time when I go to the doctor for a routine physical.

He checks my heart rate; I already know mine. He checks my blood pressure: ditto. He listens to my lungs; I ride a bike so I'm quite familiar with how my lungs sound. He peers inside my ears and down my throat, checks my reflexes, we chat for a few minutes... and off I go.

Maybe I'm being cynical, but if you pay attention to your diet and exercise, a routine physical doesn't seem necessary -- especially since I passed one with flying colors just two weeks before I had a heart attack. (Although to be fair no routine physical could have predicted that would happen.)

So that's why the American Heart Association now says aerobic fitness should be added to the list of vital signs, joining pulse, blood pressure, body temperature, and breathing rate.

The reasoning is simple: fitness levels can be a better indicator of your risk of heart disease or premature death than common risk factors like obesity, high blood pressure, and smoking. (In my case that would be true since I don't smoke, am not overweight, and don't have high blood pressure.) The AHA recommends that aerobic fitness should be evaluated during medical exams and your doctor should advise you to start exercising if your fitness level is relatively low.

And the AHA says that if your doctor doesn't start assessing your fitness level, you should do it yourself by at the very least using a scientifically-validated online tool.

Gretchen Ruben of the New York Times writes that Dr. Chip Lavie, a cardiologist and exercise scientist at the Ochsner Heart and Vascular Institute in Louisiana and statement co-author, suggests using this online fitness calculator.

So I did.

The results are interesting, but as with most online tools, somewhat limited. The first few screens ask for basic information; I'm 56 years old, 6' tall, and weigh 166 pounds. I let the tool calculate my max heart rate and was told mine is 177 beats per minute. That number was a tad disconcerting since I use a heart rate monitor when I ride and mine sometimes spikes at around 200 bpm.

Then the tool asks for workout habits. I work out pretty much every day -- I lift for close to an hour five or six times a week and ride a bike or do another form of cardio for one to two hours at least four days a week -- but the highest category on the tool is "more than thirty minutes." Then it asks for your resting heart rate (mine is 50 bpm) before getting really personal and requesting your waistline (mine is 32").

And here were my results:

  • I'm 56 years old (thanks for reminding me) and have an expected VO2 max of 42, but
  • The tool says I have the fitness level of an under 20 year-old and my VO2 max is 56.

How accurate are those results? Somewhat, I suppose. When I get out of bed in the morning, being 20 feels like a distant dream. And my VO2 max -- the maximal volume of oxygen that can be inhaled and absorbed by a body -- is actually 68.

The difference between estimated and actual VO2 max makes sense, if only because perceived levels of effort can vary. The online tool asks whether, when you work out, you "Take it easy without breathing hard or sweating" or "Little hard breathing and sweating," or "I go all out."

But your "all out" may be my "little hard breathing and sweating," just like my "all out" may be Chris Froome's "take it easy."

But still: anyone who works out regularly should know whether they train hard or train easy. I entered "go all out" because when I lift I do most sets to failure, and when I ride a bike I often throw in a few mountain climbs that feel like hot death... so at least for me, that's a lot closer to "all out" than to a little hard breathing and a light sweat.

So for a tool that takes a couple minutes to use, the result is at least directionally accurate -- and should give you an idea of whether you need to start exercising more.

And that's all that really matters -- and may be as important as knowing the other results from a routine physical. In fact, if you're out of shape you may be at greater risk of developing heart disease than if you Type 2 diabetes, or smoke, or have a high body mass index, or relatively poor cholesterol results.

Improving your cardiovascular fitness really can do wonders for your physical and your emotional health. And it can definitely help you live longer.

Reasons enough to start taking how you exercise a lot more seriously -- whether your doctor assesses your cardiovascular fitness or not.